Constance Nenni died after having a "phantom" knee surgery, according to a legal complaint filed against her orthopedic surgeon, Dr. Spyros Panos.

In March 2010, Nenni underwent surgery to repair a left knee that had grown arthritic from 76 years of wear and tear, her daughter Debra Nenni McNamee said. She died less than 24 hours after having surgery.

McNamee said she recalled Panos explaining the procedure as "a simple in and out." He asked her mother sign a consent form to have a scope with a camera surgically inserted in her knee and to remove any dead or damaged tissue he found. Then, McNamee said she sat for two hours in the waiting room of the Hudson Valley Center at Saint Francis Hospital in Poughkeepsie, N.Y., waiting for her mother to come out of surgery.

"Afterwards, a nurse came out and said that my mother's blood pressure had dropped so they had to put her under a heating blanket for a while, but she didn't seem concerned so I relaxed," she said.

Less than 24 hours later, Nenni collapsed and died at home on the bathroom floor of a pulmonary embolism, according to a medical examiner's report.

A pulmonary embolism is a dangerous side effect of surgery where a blood clot breaks free and blocks the lung's main artery. Older people are especially vulnerable to this risk. Although McNamee didn't know it at the time, she said doctors later told her that a drop in blood pressure can be a warning sign that the condition is developing.

But Brian Brown, McNamee's lawyer, said the medical examiner's report also revealed some shocking news: Panos never performed a single procedure on Nenni.

Despite writing post-operative notes stating that he had performed six procedures on Nenni, including the removal of torn cartilage, smoothing areas of arthritic wear and removal of soft tissue from within the knee joint, the autopsy and hospital records revealed Panos did none of those things.

"He put her under anesthesia, placed the scope in her knee and then closed her up without performing any surgery," Brown said. "The reports showed no hardware in place and, certainly, no evidence of a total knee reconstruction."

If true, it didn't appear to be an isolated incident. There have been at least 250 legal actions filed against Panos in state Supreme Court of Dutchess County, N.Y., noted JT Wisell, an attorney for 154 of the plaintiffs.

Panos is also the subject of a criminal investigation by the U.S. Attorney's Office, though he has not been charged with a criminal offense, Wisell said.

Wisell said that most of the pending legal cases against Panos fall into three broad categories: fraudulent surgeries like Nenni's, unnecessary or excessive procedures, and medical negligence.

Jeffery Feldman, Panos' attorney, said that it would be unethical to speak about matters currently under litigation and that he had no comment. He added that Panos could not be reached for comment.

The Mid Hudson Medical Group is named as a defendant in many of the legal cases against Panos. So, too, are the hospitals where he performed surgery, Saint Francis Hospital and Vassar Medical center, both located in Poughkeepsie, N.Y.

Lawyers for the Mid Hudson Medical Group and Vassar Medical Center declined to comment. Larry Hughes, a spokesman for Saint Francis Hospital said the hospital also declined to comment.

Brown said that Panos used his patients like human cash registers, scheduling as many as 22 surgeries a day. The average orthopedic surgeon typically schedules no more than 32 procedures a month, according to American Academy of Orthopaedic Surgeons statistics.

McNamee said the bills for her mother's care were more than $50,000. She also received a bill from Mid Hudson for her mother's post-operative follow up -- more than two years after her mother had passed away.

"We lost her because someone was looking to make money on her," McNamee said. "He took an oath to care for people not to kill people and cover it up."

Wisell, who referred to Panos as "The Hudson Valley Hack," agreed that Panos was after money. He also said he is certain other medical professionals knew Panos was scheduling too many surgeries and should have spoken up.

"I'm a million percent sure that the proper safeguards were put in place but they were completely ignored," Wisell said. "His employers and colleagues had to know what he was doing but there was too much money at stake so they looked the other way."

Both Brown and Wisell noted that clients with potential cases against Panos began flooding their offices with calls immediately after journalist Sarah Bradshaw wrote about the first few lawsuits for the Poughkeepsie Journal in September 2010. Bradshaw said she was tipped off to the litigation from an anonymous source.

Panos is currently licensed to practice in New York State and the New York State Office of Medical Conduct does not list him in its database of professional misconduct and physician discipline. The Medical Conduct Office did not immediately have an answer for why Panos was not in its system.

Panos appeared to be blogging and maintaining active Facebook page and Twitter accounts until at least July 2012.

In one blog post, he wrote that a patient once referred to him as a "21st century Marcus Welby," and that he is, "in fact, humanizing medical care and treatment." In another post, he stressed the importance of pre-operative care for better patient outcomes.